The present invention relates generally to electronic article surveillance (EAS) systems and more particularly to a novel EAS marker for use in an EAS system.
The problem of protecting articles of merchandise and the like against theft has been the subject of numerous technical approaches. One such type of approach has been to attach to the article an electronic tag or marker that is adapted to trigger an alarm or the like if the article of merchandise is moved beyond a predetermined location and the electronic marker has not been deactivated or removed from the article of merchandise. In the aforementioned type of approach, a transmitting apparatus and a receiving apparatus are typically situated on opposite sides of a passageway leading to an exit of the premises being protected, the transmitting apparatus and the receiving apparatus together defining an interrogation zone. The transmitting apparatus is typically used to transmit over the interrogation zone an interrogation signal that is recognizable by the EAS marker and that causes the EAS marker, if activated, to emit a response signal. The receiving apparatus is typically used to detect the presence of a response signal from an activated EAS marker located within the interrogation zone. The detection by the receiving apparatus of a response signal indicates that the EAS marker has not been removed or deactivated and that the article bearing the marker may not have been paid for or properly checked out. Typically, the detection of such a response signal by the receiving apparatus triggers an alarm.
Several different types of EAS markers have been disclosed in the literature and are in use. In one type of EAS marker, the functional portion of the marker consists of either an antenna and diode or an antenna and capacitors forming a resonant circuit. When placed in an electromagnetic interrogation zone created by the transmitting apparatus, the antenna-diode marker generates harmonics of the interrogation frequency in a receiving antenna in the receiving apparatus; the resonant circuit marker causes an increase in absorption of the transmitted signal so as to reduce the signal in the receiving apparatus. The detection of the harmonic or signal level change indicates the presence of the marker in the interrogation zone. With this type of system, the marker is not amenable to deactivation and, therefore, must be removed from the article of merchandise at the time of purchase so as not to trigger the alarm when the merchandise is removed from the store.
Examples of the aforementioned type of EAS marker are disclosed in U.S. Pat. No. 3,974,581, inventors Martens et al., which issued Aug. 17, 1976, and U.S. Pat. No. 4,774,504, inventor Hartings, which issued Sep. 27, 1988, both of which are incorporated herein by reference.
Another type of EAS marker includes a magnetostrictive element, also referred to in the art as “a resonator.” Typically, the resonator is in the form of a ribbon-shaped length of an amorphous magnetostrictive ferromagnetic material. Said type of EAS marker also typically includes a biasing magnetic element. The resonator is fabricated such that it is mechanically resonant at a predetermined frequency when the biasing element has been magnetized to a certain level and the resonator is brought into an interrogation zone consisting of an AC magnetic field of the predetermined frequency. In use, the biasing element is activated, i.e., magnetized, and the marker is brought into the interrogation zone, thereby causing the resonator to mechanically resonate at the predetermined frequency. This resonant signal radiated by the resonator is then detected by circuitry provided in the receiving apparatus. By demagnetizing the biasing element, the bias is removed from the resonator; accordingly, when subjected to the AC magnetic field, the resonator no longer resonates to produce a detectable magnetic field. The marker can thus be activated and deactivated by magnetizing and demagnetizing the biasing element.
Examples of the aforementioned magnetomechanical type of EAS marker are disclosed in the following U.S. patents, all of which are incorporated herein by reference: U.S. Pat. No. 4,510,489, inventors Anderson, III et al., which issued Apr. 9, 1985; U.S. Pat. No. 4,510,490, inventors Anderson, III et al., which issued Apr. 9, 1985; U.S. Pat. No. 4,622,543, inventors Anderson, III et al., which issued Nov. 11, 1986; U.S. Pat. No. 5,351,033, inventors Liu et al., which issued Sep. 27, 1994; U.S. Pat. No. 5,469,140, inventors Liu et al., which issued Nov. 21, 1995; U.S. Pat. No. 5,495,230, inventor Lian, which issued Feb. 27, 1996; U.S. Pat. No. 5,568,125, inventor Liu, which issued Oct. 22, 1996; U.S. Pat. No. 5,676,767, inventors Liu et al., which issued Oct. 14, 1997; U.S. Pat. No. 5,499,015, inventors Winkler et al., which issued Mar. 12, 1996; U.S. Pat. No. 5,565,849, inventors Ho et al., which issued Oct. 15, 1996; U.S. Pat. No. 5,494,550, inventor Benge, which issued Feb. 27, 1996; U.S. Pat. No. 5,357,240, inventors Sanford et al., which issued Oct. 18, 1994; and U.S. Pat. No. 6,067,016, inventors Deschenes et al., which issued May 23, 2000.
Another example of the aforementioned magnetomechanical EAS marker, which type is also one of the most widely used types of magnetomechanical EAS markers, comprises a plastic sheet material (e.g., styrene) which carries a heat seal coating. Said plastic sheet material is subjected to a thermoforming process to form a rectangular box-like housing with an open top bordered by a surrounding flange. A resonator is inserted into the housing through the open top, the resonator being curved slightly downwardly about its longitudinal axis. A clear, flexible, plastic sheet (e.g., polyethylene), often referred to as “lidstock,” is placed over the top of the housing and is heat-sealed or laminated to the border flange so as to close the housing, thereby encasing the resonator therewithin. Due to the aforementioned process of laminating the lidstock to the housing, a downward curve or “pillow” is typically formed in the midsection of the lidstock, said pillow delimiting upward movement of the resonator within the housing. A double-sided adhesively-coated carrier sheet is laid down over the lidstock and is secured to the border flange of the housing. A biasing magnetic element is secured to the underside of the carrier sheet. A peelable liner is applied to the top surface of the carrier sheet. When using the marker, the liner is peeled from the carrier and the exposed adhesive surface thereof is pressed against a desired article of merchandise, thereby securing the article and the marker together. Typically, the marker is manufactured as part of a batch using a multi-stationed, turntable-containing apparatus analogous to that described in U.S. Pat. No. 5,357,240. A commercial embodiment of the aforementioned marker is sold by Sensormatic Electronics Corporation (Deerfield Beach, Fla.) under the “UltraMax” trademark.
In U.S. Pat. No. 5,949,336, inventors Deschenes et al., which issued Sep. 7, 1999, and which is incorporated herein by reference, there is disclosed a fastener assembly for use in tagging an article of commerce and in detecting the unauthorized removal of the article from a store or other business establishment. The fastener assembly comprises a plastic fastener comprising an elongated filament having a first end and a second end, a transverse bar disposed at the first end of the elongated filament and a paddle disposed at the second end of the elongated filament. The paddle is shaped to include a recess. The fastener assembly also comprises an electronic article surveillance (EAS) security device which is disposed within the recess of the paddle. A cover is mounted over the recess so as to trap the security device within the paddle. A method of manufacturing the fastener assembly can be accomplished by continuously molding a length of fastener stock to form a plastic fastener having a recess formed therein, disposing a security device within the recess of the plastic fastener and mounting a cover over the recess so as to trap the security device within the fastener.
Other documents of interest include the following U.S. patents, all of which are incorporated herein by reference: U.S. Pat. No. 5,631,631, inventor Deschenes et al., which issued May 20, 1997; U.S. Pat. No. 5,717,382, inventor Cooper, which issued Feb. 10, 1998; U.S. Pat. No. 4,603,326, inventor Freed, which issued Jul. 29, 1986; U.S. Pat. No. 6,025,781, inventor Deschenes, which issued Feb. 15, 2000; and U.S. Pat. No. 6,064,306, inventors Deschenes et al., which issued May 16, 2000.